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Take-over performance in evasive manoeuvresHappee, Riender, Gold, Christian, Radlmayr, Jonas, Hergeth, Sebastian, Bengler, Klaus 30 September 2020 (has links)
We investigated after effects of automation in take-over scenarios in a high-end moving-base driving simulator. Drivers performed evasive manoeuvres encountering a blocked lane in highway driving. We compared the performance of drivers 1) during manual driving, 2) after automated driving with eyes on the road while performing the cognitively demanding n-back task, and 3) after automated driving with eyes off the road performing the visually demanding SuRT task.
Both minimum time to collision (TTC) and minimum clearance towards the obstacle disclosed a substantial number of near miss events and are regarded as valuable surrogate safety metrics in evasive manoeuvres. TTC proved highly sensitive to the applied definition of colliding paths, and we prefer robust solutions using lane position while disregarding heading. The extended time to collision (ETTC) which takes into account acceleration was close to the more robust conventional TTC.
In line with other publications, the initial steering or braking intervention was delayed after using automation compared to manual driving. This resulted in lower TTC values and stronger steering and braking actions. Using automation, effects of cognitive distraction were similar to visual distraction for the intervention time with effects on the surrogate safety metric TTC being larger with visual distraction. However the precision of the evasive manoeuvres was hardly affected with a similar clearance towards the obstacle, similar overshoots and similar excursions to the hard shoulder.
Further research is needed to validate and complement the current simulator based results with human behaviour in real world driving conditions. Experiments with real vehicles can disclose possible systematic differences in behaviour, and naturalistic data can serve to validate surrogate safety measures like TTC and obstacle clearance in evasive manoeuvres.
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Design and Analysis of Flexible Biodiesel Processes with Multiple FeedstocksPokoo-Aikins, Grace Amarachukwu 2010 August 1900 (has links)
With the growing interest in converting a wide variety of biomass-based
feedstocks to biofuels, there is a need to develop effective procedures for the design and
optimization of multi-feedstock biorefineries. The unifying goal of this work is the
development of systematic methodologies and procedures for designing flexible multifeedstock
biorefineries. This work addresses four problems that constitute building
blocks towards achieving the unifying goal of the dissertation.
The first problem addresses the design and techno-economic analysis of an
integrated system for the production of biodiesel from algal oil. With the sequestration
of carbon dioxide from power plant flue gases, algae growth and processing has the
potential to reduce greenhouse gas emissions. Algae are a non-food oil feedstock source
and various pathways and technologies for obtaining algal oil were investigated.
Detailed economic and sensitivity analysis reveal specific scenarios that lead to
profitability of algal oil as an alternative feedstock. In the second problem, a new safety metric is introduced and utilized in process
design and selection. A case study was solved to assess the potential of producing
biodiesel from sewage sludge. The entire process was evaluated based on multiple
criteria including cost, technology and safety.
The third problem is concerned with incorporating flexibility in the design phase
of the development of multi-feedstock biofuel production processes. A mathematical
formulation is developed for determining the optimal flexible design for a biorefinery
that is to accommodate the use of multiple feedstocks. Various objective functions may
be utilized for the flexible plant depending on the purpose of the flexibility analysis and
a case study is presented to demonstrate one such objective function.
Finally, the development of a systematic procedure for incorporating flexibility
and heat integration in the design phase of a flexible feedstock production process is
introduced for the fourth problem. A mathematical formulation is developed for use in
determining the heat exchange network design. By incorporating the feedstock scenarios
under investigation, a mixed integer linear program is generated and a flexible heat
exchange network scheme can be developed. The solution provides for a network that
can accommodate the heating and cooling demands of the various scenarios while
meeting minimum utility targets.
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